In recent years, ground subsidence due to various causes has been affecting concrete slabs, which serve as the substructure for building structures, such as factories, warehouses, stores, and houses, and civil engineering structures, such as roads, docks and ports, bridges, and airports, resulting in problematic damages. When ground subsidence occurs due to, for example, a pumping of a large amount of underground water as factory water from a weak ground zone, an upwelling of a large amount of water resulting from the development of underground tunnels, insufficient compaction of the soil on reclaimed land from the ocean or large-scale developed land, or the like, concrete slabs are inclined. This causes problems in that the behavior of machines installed in the building structure is affected, or shelves are inclined, obstructing the cargo handling work. In addition, when cracking occurs due to the inclination of a concrete slab, this causes a situation where vehicles and carts cannot run. As a method for modifying a concrete slab to deal with these problems, a method in which an expandable resin is injected into an inside of subsided ground or a space formed between the ground and a concrete slab, and the expandable resin is expanded to push up the concrete slab to a predetermined height, is known (e.g., Patent Document 1).